ES2251622T3 - USE OF A MATERIAL BASED ON ORGANIC, AND / OR ORGANIC AND CHITOSAN FIBERS FOR THE FIXATION OF METAL IONS. - Google Patents

Abstract

The invention concerns the use of a material based on organic and/or inorganic fibres and chitosan for fixing metal ions contained in an effluent. The invention is characterised in that chitosan represents between 0.01 and 20% by dry weight of fibres and its degree of deacetylation is higher than 90%.

Description

Use of a fiber-based material organic, and / or inorganic and chitosan for ion fixation metallic

The invention relates to the use of a material based on organic and / or inorganic fibers and chitosan for fixing metal ions contained in a liquid or solid effluent. Among the effluents containing metal ions in significant proportions, or in the trace state if a treatment was previously carried out, effluents from, in particular, the mining, nuclear, chemical, surface treatment industry, but particularly also agricultural, for example, the pig slurry or also the sludge used as fertilizers and from the purification stations without, in any way, this list is
limiting

In the following description and in the successive claims, by the expression "organic fibers and / or inorganic "is designated among organic fibers, in particular cellulosic fibers, synthetic fibers of the type, for example, Polyester or polyethylene, polypropylene, polyamide, polychloride vinyl; artificial fibers (for example, viscose, acetate cellulose); natural fibers (for example, cotton, wool, pulp of wood); carbon fibers (occasionally active) and between inorganic fibers, in particular mineral fibers (for example, glass, ceramics).

Chitosan is a product of deacetylation of the chitina, constitutive element of the shells of crabs, lobsters, shrimp and other crustaceans. By way of known, chitosan has complexing properties of ions metallic, in pH values greater than 4.

Document WP 80/02708 describes a purification process of contaminated aqueous effluents, in particular of effluents rich in heavy metals, by means of Chitosan under microcrystalline form, that is modified. Plus precisely, the microcrystalline chitosan is incorporated into a gel-like dispersion, which comes into contact with a contaminated aqueous effluent. After stirring at temperature elevated, the chitosan complexed with the contaminant separates from the solution by filtration, sedimentation, centrifugation or Any suitable procedure. In addition, it should be noted that the Chitosan has a degree of deacetylation greater than 30%. Had account of the microcrystalline form of chitosan, you can expect that its functions -NH_ {2} are involved within the network crystalline, so they are not available for complexation metallic It follows that the decontamination technique described in this document is not optimal.

GB-2 199 315 describes a support structure based on source fibers microbiological treated in alkaline solution so that it Detect the chitina it contains. According to the described procedure, the Mycelium culture is treated in alkaline medium before or after be deposited on a structure of synthetic fibers of the type polyester or polypropylene.

JP 08 13 2037 describes a water purifier, which associates chitosan and low activated carbon granulated form in a ratio of 1:20. Although it has been indicated that the mixture can absorb heavy metals, not provided No quantitative information. In effect, the set of results are expressed in relation to the capacity of the purifier to eliminate the chlorine contained in the city water.

JP 83 04 9212 describes an absorbent filter consisting of cellulose, diatom or perlite and chitosan fibers. The cellulosic fibers and diatoms are mixed in a ratio of 4 / 1-1 / 4 by weight and then chitosan is added, diluted in acid solution at a rate of 10% by weight. The filter is used here for the separation of colloidal proteins, micro-particles and mushrooms. No information was provided as to the possibility of using this material for fixing heavy metals. Even if it was used for this application, its efficacy would be lower since diatoms or perlite contain proteins that can interact with the chitosan amine functions. In this case, the complexing properties of metals by the chitosan will result
affected.

EP-A-0 323 732 describes, on the other hand, a composite material based on cellulose fibers, chitosan (at a rate of 1 to 99% by weight) and fatty acids (0.05 to 1% with respect to to the weight of cellulose fibers). According to an essential characteristic, the chitosan used in this composite material has a degree of deacetylation of at least 40%. At such rate, and according to this document, chitosan allows to improve the strength of the paper, particularly in the wet state. No mention is made as to the possibility of using this material for the fixation of heavy metals present for example in an aqueous effluent. Even if this material was used for such an application, its effectiveness would be small. In fact, the hydrophobic character that the fatty acid confers on the treated paper influences the kinetics of water sorption. By slowing the diffusion of water within the support, fatty acid also decreases the ability to complex. The accessibility of the chitosan is then
diminished

GB 2 336 477 describes a support with base of cellulosic and chemical fibers coated with chitosan a ratio of 3 to 20% by weight. No indication is mentioned Regarding the characteristics of chitosan. The support is used for fixing, for example, arsenic type metal ions, iron sulfate and magnesium chloride (examples 6 to 8). If he Illustrated support has a good ability to complex metal ions, it is only for effluent flows very small and in any case, incompatible with an application industrial.

Document GA-2 165 865 describes the use of chitin / chitosan ( Hyphae ) producing microorganisms treated in alkaline solution to reveal their constituents and then their association with other fibers to form materials useful for capturing metal ions.

The problem trying to solve the invention It is, therefore, to improve the rate of fixation of ions metallic and consequently, the effluent flow that is going to try. However, the applicant has found that the speed of metal ion fixation could be increased when combined a small chitosan concentration with a degree of deceleration raised higher than 90%.

Accordingly, the invention relates to the use of a material based on organic fibers and / or inorganic and chitosan for fixing metal ions contained in an effluent, characterized in that the Chitosan represents between 0.01 and 20% dry weight of the fiber, because it represents a degree of deceleration greater than 90% and because the material is presented in the form of a sheet obtained by paper after mixing the chitosan with the fibers organic and / or inorganic. With the deacetylation of chitosan it significantly modifies the kinetics of ion fixation metallic If this situation could be achieved by increasing the number of available chitosan sites by deacetylation, the fixing capacity is not being evident, because of the on the contrary, that the fixing speed be improved at the same weather.

The fixation of the metal ions contained in An effluent can find several applications. One of these applications can be, in principle, fixing heavy metals contained in a liquid effluent. Therefore, the material is used, in this case, for the filtration of liquid effluents by grout or watertight crossing depending on the degree of contamination of the effluent. Another application may be the fixation of ions metal present in the ground, in particular, after copper-based chemical treatment, for example, of a agricultural area In this case, the material that can correspond to a soaking paper is used to fix the ions metallic and thus prevent them from entering the water table. By Finally, it can be the voluntary fixation of metal ions on the material of the invention, either to improve its conductive properties, either to form a metallic layer by reduction of fixed metal ions, either to make said material has biocidal properties.

In an advantageous embodiment, the chitosan It has a degree of decelitation greater than 95%.

In practice, the chitosan presents a weight Molecular between 10 4 and 10 6 g.mol -1. preferably between 10 5 and 5.10 6 g.mol -1.

In an advantageous embodiment, the Chitosan represents between 0.01 and 10%, preferably between 0.01 and 5% and optically between 0.01 and 2% dry weight of the fibers

As stated above, the material is a organic and / or inorganic fiber base, but may be advantageously constituted by cellulose fibers. According to invention, chitosan is mixed with organic fibers and / or inorganic and then a sheet is formed by paper.

In practice, chitosan is used initially in the form of salt (acetate, hydrochloride, etc.).

The invention finds an application particularly advantageous in the treatment of drinking water, of effluents from, in particular, the mining industry, nuclear, chemical, surface treatment, but also, agricultural, such as pig slurry or sludge from spreading as fertilizers and coming from the seasons of debugging, without this list being limiting.

The invention and the derived advantages are they will know better through the realization examples following.

Figure 1 represents the fixation kinetics of copper by chitosan alone and the material of the invention with a copper concentration of 0.3125 mg / l.

Figure 2 represents the fixation kinetics of copper by chitosan alone and the material of the invention with a 0.625 mg / l copper concentration.

Figure 3 represents the fixation kinetics of copper by chitosan alone and the material of the invention with a copper concentration of 3,125 mg / l.

Figure 4 represents the influence of the proportion of chitosan in the material of the invention versus the fixation of copper ions.

Example one

In this example, the kinetics of fixation of copper on chitosan alone and on the material of the invention, the chitosan mass being 50 mg, in conditions static, that is without effluent flow through the filter.

a / Chitosan

The chitosan used has a molecular weight equal to 200,000 g / mol and a degree of deacetylation of 98%.

b / Material of the invention

A sheet based on cellulosic fibers is coated with chitosan solution, using the technique of bed deposit, so that a support containing 2% chitosan by weight.

c / Protocol

-

he Chitosan alone or deposited on paper is hydrated for 12 hours in 100 ml of a NaNO 3 effluent (0.03 M) with a pH 6.5,

-

be add a volume V of a copper stock solution,

-

be extract material swimming at different times,

-

be dose by I.C.P. (Inductive coupled plasma),

-

by Finally, the decontamination factor is calculated, which corresponds to the initial concentration / concentration ratio end in the effluent.

From this factor the more or less good is deduced decontamination function of chitosan alone or of the material of the invention based on the following scale:

FD = 1: Without decontamination

FD = 7/8: Good decontamination

FD> = 1: Very good decontamination

The study is conducted for concentrations in copper decreasing.

As illustrated in Figure 1, after 210 minutes, 98% of the copper is fixed on the coated paper of chitosan, while 13% only look at the chitosan only for a copper concentration of 0.3125 mg / l.

Figure 2 illustrates that, for a concentration in 0.625 mg / l copper, chitosan coated paper has already set a 82% copper, while, at the same time, the film of Chitosan has set 31% copper only.

Finally, for a copper concentration of equal to 3,125 mg / l, 75% copper is fixed on paper coated after 360 minutes, while only 12% of Copper is fixed on the chitosan alone (Figure 3).

Decontamination factors are calculated and they represent in the attached Table.

Concentration on copper in mg / l Chitosan alone Material invention 6.35 Decontamination negligible 1.1 3,176 1.07 1.43 0.835 1.2 3.5 0.3175 1.4 9.7

It is thus observed that the fixing capacity of the Copper for the material of the invention is superior to that of chitosan only and this for all the concentrations tested. By On the other hand, it is verified that the fixing kinetics of copper on the chitosan is only less rapid than for the material of the invention.

Indeed, for a copper concentration of 3,125 mg / l, the decontamination factor of 1.07, obtained after 180 minutes for the chitosan alone, it is obtained only after 4 minutes for the material of the invention.

In the same way, for a concentration on 0.625 mg / l copper, the decontamination factor of 1.2, obtained after 90 minutes for the chitosan alone, it is obtained after only 8 minutes with the material of the invention.

For a copper concentration of 0.3125 mg / l, the decontamination factor of 1.4, obtained after 200 minutes with the chitosan alone, you get after just 20 minutes with the role of the invention.

Example 2

In this example, the influence of the proportion of chitosan in a cellulose sheet versus its capacity of fixation of copper ions.

As illustrated in Figure 4, the weaker is the proportion of chitosan the better is the fixing capacity of the material of the invention of copper ions within the range studied.

Example 3

In this example, the effectiveness of Dynamic invention filter for effluent flow high.

The filtration system used is the filter-press the most common and simple equipment in the field of filtration of liquids. The effluent is purified in the moment of its passage through the filter medium constituted by a succession of filters. The number of consecutive filters can adapt according to the performance sought. In this studio, each 550 cm2 surface filter consists of a paper 100 g / m2 of grammage, containing 1% chitosan en masse of the degree of deacetylation equal to 98%.

The effluent model used is a solution of 6.35 mg / l copper that passes through the filter medium with a flow of 4200 l / h, the volume of effluent being 10 liters rehearsed

The rate of copper withheld, depending on the number of filters used to constitute the filter medium, Represents in the following table.

Number of filters 4 8 10 Copper rate detained 64% 57% 70%

With 10 filters, 70% of copper is set to less 9 seconds

Example 4

In this example, it is compared in dynamics, in the same conditions as in example 3, the influence of quantity of chitosan in the filter paper for concentrations of 1 and 5%. The degree of deacetylation is 98%.

% chitosan Number of Copper rate Quantity from Amount of Fixing rate from filters content copper detained chitosan copper over the chitosan one 4 64% 41 mg 0.2 g twenty% 6 4 68% 43 mg 1 g 4 g

As indicated in the previous table, the higher is the amount of chitosan in the fork tested so much weaker and the higher the fixing efficiency will be.

Claims (5)

1. Use of a material based on organic and / or inorganic fibers and chitosan for fixing metal ions contained in an effluent, characterized in that:

-

he chitosan represents between 0.01 and 20% dry weight of the fiber;

-

he Chitosan deacetylation degree is greater than 90%;

-

he material is presented in the form of a sheet obtained by way wastebasket after mixing chitosan with organic fibers and / or inorganic.

2. Use according to claim 1, characterized in that the chitosan molecular weight is between 10 4 and 10 6 g.mol -1. 3. Use according to claim 1, characterized in that the chitosan represents between 0.01 and 10% by dry weight of the fibers, preferably between 0.01 and 2%. 4. Use according to claim 1, characterized in that the degree of deacetylation of chitosan is greater than 95%. 5. Use according to claim 1, characterized in that the sheet exclusively contains cellulose fibers.